The present invention relates to a system and a method for producing circuit boards on which electronic components are mounted after having solder printed thereon.
FIG. 22 is a structural block diagram of a conventional system 216 for producing electronic component-mounted circuit boards. The system of FIG. 22 includes a solder printing section 203, an electronic component mounting section 204, and a soldering section 205. These sections are arranged sequentially down stream along a circuit board transfer line. A cream solder printing device 210 of the solder printing section 203 prints cream solder on lands of objects to be printed such as circuit boards or the like. A cream solder printing inspecting device 211 inspects the states of the circuit boards and the printing facilities, and also the printing state of the cream solder printed by the printing device 210. A data processor 220, which is connected to the inspecting device 211 and the printing device 210, analyzes the data outputted from the inspecting device 211 for feedback control of the printing device 210.
In the electronic component mounting section 204, a mounting device 212 transfers suction nozzle heads to an electronic component feeding section using an X-Y driving device, then suctions the electronic components using the suction nozzle heads, and feeds the electronic components to mounting positions where they are to be mounted on the circuit boards. The mounting device 212 mounts the electronic components so that the leads and the electrodes are positioned on the printed cream solder located on the lands. At this time, the suction state of the electronic components is viewed by an electronic component recognizing camera to evaluate the suction error. A post-mounting inspecting device 213 inspects the electronic components mounted at predetermined positions on the circuit boards and also the operating state of the facilities. A data processor 221, which is connected to the post-mounting inspecting device 213 and to the mounting device 212, analyzes the data from the post-mounting inspecting device 213, to thereby effect feed-back control of the mounting device 212.
Further, in the soldering section 205, a conveyor is arranged in a reflow furnace 214 to transfer the circuit boards to be heated in the furnace. Heaters are placed above and below the conveyor, having upper and lower fans. Hot wind of heated gas is blown onto the circuit boards by the fans. The interior of the reflow furnace 214 is sectioned into a preheating chamber, a reflow heating chamber, and a gradual-cooling chamber. The above heaters and fans are provided in each chamber. The electronic components are soldered to the circuit boards by the reflow of the cream solder when the circuit boards are uniformly heated in the reflow heating chamber. A soldering inspecting device 215 inspects the soldering state of the electronic components on the circuit boards and the operating state of the facilities. A data processor 222, which is connected to the soldering inspecting device 215 and to the reflow furnace 214 analyzes the data of the inspecting device 215 to thereby affect feed-back control of the reflow furnace 214.
The operation of the producing system 216 will now be described. In the first place, cream solder is printed by the cream solder printing device 210 on the land of a circuit board. The state of the circuit board and the facilities, and the printing state of the cream solder on the land (for example, whether the cream solder is blurred or thinned or shifted, or the presence/absence of printing of the cream solder, etc.) are inspected by the inspecting device 211. The output data from the inspecting device 211 is analyzed by the data processor 220, whereby the printing device 210 is controlled to restrict the generation of defective products.
Subsequently, the mounting device 212 transfers the suction nozzle head to the electronic component feeding section using an X-Y driving device to suction and move the electronic component to the mounting position of the circuit board. The electronic component is applied to a predetermined position of the circuit board and mounted by utilization of the viscosity of the cream solder on the land. The state or condition of the mounting device 212, and the mounting state of the electronic component (e.g., an absence of the electronic component, an improper orientation of the component, a shift of the mounting position, an erroneous mounting in polarity, or the like) are inspected by the post-mounting inspecting device 213. The data outputted from the inspecting device 213 is analyzed in the data processor 221, to thereby control the mounting device 212 to prevent the generation of defective products.
The circuit boards are transferred into the reflow furnace 214 by the conveyer. When the hot gas is blown onto the circuit board by the fans, the circuit board is preliminarily heated and the printed cream solder on the land is reflowed in the reflow heating chamber and then gradually cooled. As a result, the leads or the electrodes of the electronic component are soldered to the land of the circuit board. The inspecting device 215 inspects the state of the reflow furnace 214 and the soldering state of the electronic component on the circuit board (e.g., an absence of the electronic component, an improper orientation of the component, a shift of the mounting position, an erroneous mounting in polarity, or the like). The data of the inspecting device 215 is fed back after being analyzed by the data processor 222 to control the reflow furnace 214 to restrict the generation of defective products.
Conventionally, in the case where the circuit board is detected as being defective in the solder printing section 203, the electronic component mounting section 204, or the soldering section 205, the circuit board is discharged or corrected.
In the prior art technique as above, the data from the inspecting devices 211, 213, and 215 are analyzed by the corresponding processors 220, 221, and 222 and fed back to avoid the generation of defective products. However, when the electronic components are mounted at a high density on the circuit board, the causes of circuit board defects is complex and related to numerous processes and items to be monitored. Therefore, it is not sufficient simply to carry out feed-back control for each section individually.
Referring again to FIG. 22, the printed circuit board manufacturing section 201 and the screen manufacturing section 202 are arranged at the upstream of the transfer line relative to the solder printing section 203. In the printed circuit board manufacturing section 201, a printed circuit board manufacturing device 206 forms a circuit pattern having a land pattern on the board. A printed circuit board inspecting device 207 inspects the position and the shape of the land of the printed circuit board and the state of the circuit pattern, etc. In the screen manufacturing section 202, on the other hand, a screen generator 208 forms a screen to be used in printing of the cream solder in the solder printing section 203. A screen inspecting device 209 inspects the position and the shape of the pattern of the screen and the state of the circuit pattern, etc.
Conventionally, the inspecting data used as reference data, such as target values, allowable ranges, inspecting conditions or the like to operate each inspecting device 207, 209, 211, 213, and 215, are formed through learning of the X-Y coordinates, the mask data, and the land data of the actual printed circuit board. Although CAD data may sometimes be partly employed as mounting data, only the restricted data such as X-Y coordinates or the like are used, with an aim of efficiently forming the data by reducing the number of inputs by the operator.
FIGS. 23A and 23B illustrate the manner in which the inspecting data is formed in the prior art. As shown in FIG. 23A, in forming the inspecting data, conventionally, command codes of each electronic component to be inspected are sequentially determined and inputted manually with reference to the basic data related to each land to be printed (namely, the name, position, and posture of the land), the basic data related to an electronic component corresponding to the to-be-inspected land (i.e., name, position, and posture of the electronic component), and a command code table formed from a table which is formed based on a machine data corresponding to each data after the allowable values at the time of inspection based on the above basic data are selected.
In another technique, as indicated in FIG. 23B, the circuit board which has already been detected as having correctly printed cream solder or soldered cream solder is read by a printing inspecting device or the like, and the necessary data is loaded into the inspecting device, and inspecting conditions such as the permissible values or the like are additionally inputted manually.
In the above-described arrangement, the actual inspecting data used as a reference including target values, permissible ranges, and inspecting conditions, etc. are not estimated before the circuit board is inspected and the inspecting result each time is accumulated and statistically processed. Vagueness and uncertainty exists as to whether the inspecting data formed on the basis of the irregular data of circuit boards is accurate. It is also difficult to correctly and quickly identify the nature of problems in the production line, i.e., whether the printed circuit board under inspection itself is defective or the inspecting data is improper, that is, it is difficult to promptly decide the presence/absence of a defect and the cause of the defect.
More specifically, although the ideal shape, area, and amount of the solder or the solder fillet can be assumed in the stage of design, it is not easily realized on the actual printed circuit board. As shown in FIG. 24, even in the case where the displacement (A) of the printing position between a land 217 and a printed cream solder 218 on the printed circuit board, and the displacement (B) of the mounting position between the printed cream solder 218 and an electronic component 219 on the printed circuit board is detected, it is not clear which of the land 217 and the cream solder 218 is shifted, whether the electronic component 219 or the cream solder 218 is shifted, and further whether an alignment mark is shifted. Moreover, with respect to the soldering position, it is considerably difficult to determine whether the electronic component 219 is shifted or the solder fillet is shifted, or whether the alignment mark is shifted. In this case, the operator is obliged to make a decision from his or her experience, but without guarantee that his or her decision is correct. The decision may lead to an erroneous feed-back or delay due to an unnecessary correction in the worst case.
Further, as the printed circuit board becomes more and more densely fitted, the accuracy required in each of the printed circuit board producing process, the screen producing process, the cream solder printing process, the component mounting process, and the soldering process is strict and even a slight error is not allowed. It is not possible for the conventional arrangement to meet such requirements.